Предмет: Геометрия, автор: ShkolaBezPrikola

Определи площадь такого сечения куба, которое проведено через диагонали соседних граней, имеющих общий конец — например, через диагонали BA1 и BD — если длина ребра куба составляет 9 см.

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ShkolaBezPrikola: помогите

Ответы

Автор ответа: siestarjoki

Грани куба - равные квадраты, диагонали граней равны.

△BA1D - равносторонний треугольник со стороной 9√2 см.

Его площадь √3/4 (9√2)^2 =81√3/2 (см^2)

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